FOR any follower of “the arte of the angle” – as Isaak Walton described fisherman – and particularly for those slaves to the temptations of that harsh mistress the artificial dry fly, this is an anxious weekend. Will Ephemera danica emerge? Or is Duffers’ Fortnight gone forever?
For the uninitiated, I should explain that Ephemera danica is the species name for one of our most beautiful and at the same time most tragic insects, the mayfly. And Duffers’ Fortnight is the centuries-old fly-fisherman’s nickname for – hopefully – the coming two weeks in which the said flies are supposed to hatch in their billions, thus sending trout into a feeding frenzy.
Mayfly: rare sight?
This phenomenon once sent even very large trout, long since turned cannibal, to the surface of our lakes and streams to gorge themselves on a virtual carpet of fresh delicacies and therefore made them easy to catch even by inexperienced anglers – hence the somewhat dismissive label used by older, more gnarled users of the craft (and they don’t get much older and more gnarled than me).
But please note my use of the past tense. For in recent years, the great mayfly hatches on many of our famous trout rivers – including several of the glittering limestone streams in the Yorkshire Dales – have faded so much to have almost disappeared. And the question is: why?
Some 40 years ago, when Ireland was still a reasonably cheap place to holiday, a group of friends and I made an annual pilgrimage to County Galway to spend Duffers’ Fortnight fishing mighty Lough Corrib, then advertised has having “the best game fly fishing in Europe.”
In the first two or three years, that claim was possibly justified. The mayfly hatched in such huge swarms that, when they went into their circular mating dance, it looked as though clouds of smoke were coming from the water.
That, sadly, was there one and only function in the air: after mating, the males died, the females landed back on the water to hatch their eggs and then they died too – if they had not fist been snatched up by the voracious trout cruising the surface like sharks in a blood frenzy.
Not much of a reward, one might say, for three years spent feeding on the lake bottom as an ugly, predatory nymph but that is nature red in tooth and claw: the flies hatched in such enormous quantities that plenty survived to continue the millennia old cycle and still feed millions of trout averaging about four pounds and sometimes surpassing ten – as well as thousands of birds like terns, swallows and wagtails.
And this is why I will be keeping my fingers crossed during Duffers’ Fortnight
But then, early in the 1970s, something went terribly wrong. Year on year, our catches of trout began to decline just at a time when Ireland was becoming more and more expensive as a holiday retreat. In my last year there ever, I caught just one fish – a small perch which surprisingly took a fly – and it was time to start searching for other fishy destinations.
Now what had gone wrong? I have never seen this proved scientifically, but many of my Irish angling colleagues believed it was the establishment of large pig-breeding farms on the shores of the lough. And – although this was not supposed to happen – they all claimed that pig slurry was leaching into the water in lethal quantities.
Now that tiny perch, my last ever Corrib catch, was of course a “coarse” fish i.e.: one that normally prefers slow moving, muddy waters with thick water weed – not at all like the once crystal clear limestone shallows of the Corrib. So was it the pig slurry which had somehow changed the chemical make-up of the lake?
This takes me to a process known to marine biologists known as “eutrification” or, more simply, the enrichment of fresh water from run-off farm fertilisers or manure. Just like fertiliser spread on a veg plot, it causes vegetable matter to grow and, in water in particular, a rapid bloom of minute plankton.
When this dies, it takes oxygen out of the water, leaving the bottom covered with a slimy, mud-coloured deposit, and also changes the chemical balance – just the way to swing it towards the benefit of the perch and away from the oxygen-loving trout.
And this is why I will be keeping my fingers crossed during Duffers’ Fortnight here in the Yorkshire Dales. Farmers have, of course, been spreading muck of their land for centuries and in reasonable amounts that is to be encouraged. But modern machinery and storage methods spurt out highly concentrated liquid slurry which, I am convinced, leaches quickly into our trout streams to do terribly damage.
Personally, I don’t care overmuch for Duffers’ Fortnight. It tends to attract anglers we call Fishmongers, who will thrash the water until their creels are full. As a point of conservation principle, I never take more than two fish from a day on the bank.
But these days, to get two is lucky. This clash between fertilisers and food production is one of the more urgent tasks for our new Defra ministers to tackle and, fortunately, they seem to know what they are doing. Otherwise, the ephemeral existence of Ephemera danica might be over before it even has time to hatch.